What is Ripple and Ripple Factor? Formula of Ripple Factor

Ripple factor is the ratio of AC Plus DC components to DC components in the rectified waveform. In this article, we will learn what ripple, ripple factor, ripple factor formula & its derivation.

What is Ripple?

When the AC waveform is rectified with a rectifier unit, the rectified output is not perfectly DC. Rather, the DC output has pulsating components called AC components. The pulsating components present in the DC output voltage are called the voltage ripples, and the pulsating components in the DC current are called the current ripples.

Reasons for ripples in DC output?

The rectification components like a diode, silicon-controlled rectifier, and insulated gate bipolar transistor cause the DC output to have a pulsating nature. The ripples are undesirable in the DC output, however complete elimination of it is impossible. Yes, we can reduce these to a great extent by filtering the rectified DC output voltage.

If we observe the rectified DC output of the full wave rectifier, we find that the rectified DC output is not perfectly DC rather than the rectified DC voltage or current having AC components.

waveform of ripples in dc

The output of the full wave rectifier has a pulsating voltage. The average or DC voltage reduces due to the presence of pulsating voltage in the rectified output voltage or current. The full-wave rectifier has fewer ripples than a half-wave rectifier.

Ripple Factor Definition

The ratio of the RMS value of the AC component to the DC component in the rectifier output is known as the ripple factor.

ripple factor definition

This factor is a very important parameter for assessing the effectiveness of the rectifier. The lower ripple factor value shows that the ripples in the DC output are less, and the efficiency of the rectifier is better. The higher value shows that there are more fluctuating AC components present in the rectified output.

Ripple Factor Formula

The RMS. value of rectified DC voltage is the vector sum of the AC components and DC components in the rectified output. 

ripple factor formula

Derivation of Ripple Factor Formula 

The rectified output does not have a pure DC component but an AC component as well. The AC component available in the rectified DC causes lower rectification efficiency. The load current has both AC and DC components. Let the load current be IL, and the current IL has both an AC component and a DC component(Idc).

Ripple = IL– Idc  = VL– Vdc  

Here, iL and vL are the output current and voltage through the load connected at the terminals of the rectifier. Similarly, Vdc and Idc are the average values of load voltage and current. The RMS value and the average value of the load current are given below.

The calculation of the RMS value of the rectified current is as follows.  

derivation of ripple factor formula
derivation of ripple factor formula
Derivation of ripple factor formula

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